Thermally activatable insulating packaging

ABSTRACT

A package or container includes a side wall, the side wall having an inner surface and an outer surface. At least one of the inner surface or the outer surface of the side wall may be at least partially coated by a layer of a thermally expandable material. The material may be adapted to be expanded to provide thermal insulation.

RELATED APPLICATION

The present application is a continuation application of U.S.application Ser. No. 11/728,973, filed Mar. 27, 2007, now U.S. Pat. No.9,056,712, which claims the benefit of the filing date under 35 U.S.C.§119(e) of Provisional U.S. Patent Application Ser. No. 60/789,297,filed Apr. 3, 2006, which is hereby incorporated by reference.

BACKGROUND

Consumers frequently purchase ready-made products, such as food andbeverages, in disposable containers. Thermally insulated containers maybe designed for hot or cold liquids or foods, such as hot coffee,iced-tea, or pizza. These containers may maintain the temperature of theliquid or food contents by preventing heat or cold transfer from thecontents to the consumer's hand.

BRIEF SUMMARY

A package or container includes a side wall, the side wall having aninner surface and an outer surface. At least one of the inner surface orthe outer surface of the side wall may be at least partially coated by alayer of a thermally expandable material. The material may be adapted tobe expanded to provide thermal insulation.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cup assembled with a die cut blank.

FIG. 2 is a perspective view of a cup assembled with a full-body die cutblank with openings.

FIG. 3 is a perspective view of another integrated container withchannels.

FIG. 4 is a cross section view of an assembled die cut blank.

FIG. 5 is a top perspective view of a cross section of a cup assembledwith a die cut blank.

FIG. 6 is a view of a die cut blank disassembled from a cup.

FIG. 7 is a view of a die cut blank disassembled from a cup.

FIG. 8 is a view of a die cut blank disassembled from a cup.

FIG. 9 is a view of a die cut blank disassembled from a cup.

FIG. 10 is a view of a die cut blank disassembled from a cup.

FIG. 11 is a view of a die cut blank disassembled from a cup

FIG. 12 is a view of a cup assembled with a die cut blank illustratingheat transfer.

FIG. 13 is a side cutaway view of a double-wall cup.

FIG. 14 is a block diagram of an exemplary process for applying amicro-particle coating to substrates.

FIG. 15 is a schematic of applying a coating to a substrate with spraynozzles.

FIG. 16 is a schematic of applying a coating to a substrate withnon-spray nozzles.

DETAILED DESCRIPTION

A package or container may be constructed of, and/or insulated with, adie cut blank, such as a sleeve. The die cut blank may be fixed to acontainer or it may be removable. Thermally-expandable material may beapplied to the container and/or die cut blank. Expandable materials thatare expanded in ways other than by temperature may also be used. Thematerial may be expanded before reaching an end user, such as when thecontainer and/or die cut blank are manufactured, and/or the material maybe expanded only on end use and only in response to a determinedtemperature. The material may be used to aid with insulatingcapabilities of the container and/or die cut blank, and/or to addrigidity to the container and/or the die cut blank, such as to reduce athickness of the material components of container and/or die cut blank.

FIG. 1 illustrates a container 101, such as a cup, and a die cut blank102, such as a sleeve. The container is described in terms of a cup, forexample, but may also include other containers such as a plate or tub.The blank may be in the form of a container sleeve or an outer wall tothe container. The container is not limited to a cup and may be anyother container, including but not limited to, a bulk coffee container,a soup tub, and press-formed containers, with or without covers orsleeves. The container 101 may be a cylindrical cup or a containerhaving other geometrical configurations, including conical, rectangular,etc. The die cut blank is not limited to a corrugated die cut blank, andmay be constructed of paperboard, paper, etc. The die cut blank 102 maybe made of any nominal paper stock, including but not limited to,natural single-face, white-topped single face, coated bleached topsingle-face, corrugate, fluted corrugate or any combination of these.The die cut blank 102 may be removable from the container or the die cutblank may be adhered to the container 101. The blank 102 may be adhered,for example, by laminating the die cut blank onto the container, using ahot melt, cold melt and/or any other adhesive or sealing mechanisms.Alternatively or in addition, the blank may be adhered with anexpandable material, such as a microsphere material. If the die cutblank is attached to the cup during manufacture, it may increaseefficiency by eliminating an assembly step by the commercial end-user.Further, it may decrease the amount of storage space required by thecommercial end-user, e.g., storing one item as opposed to two.

FIG. 1 is not necessarily drawn to scale. For example, the die cut blank102 may cover a larger or smaller portion of the container's 101 surfacethan illustrated. For example, the die cut blank may provide full bodycoverage. Increasing the surface area of the die cut blank 102 mayprovide a larger insulated area as well as a larger print surface.Although the drawing illustrates the die cut blank on a cup, the die cutblank may be added to any other containers, such as but not limited to,a bulk beverage container, press-formed container, and soup tub.

A thermally activatable coating may be applied between the container 101and the blank 102. The expandable material may be thermally-activatable,by a hot or cold temperature, and may be an expandable coating oradhesive, including but not limited to, binder, expandable microspheresor other micro-encapsulated particles, pigment and other additives, orany combination of these or other materials. The material may beexpandable when wet or dry. The material may include any synthetic ornatural material including aqueous based, solvent based, high solids, or100% solid materials. The amount of solid content is typically 30% to80% of the material, and more preferably 40% to 70%. Additionalingredients may be added to the binder, including but not limited to,pigments or dyes, fillers/extenders, surfactants for dispersion,thickeners or solvents to control viscosity for optimized application,defoaming agents, additives like waxes or slip aids, etc. Alternatively,the binder may be an adhesive. The expandable material may have severalproperties, including but not limited to thermal insulation to keepcontainer contents hot or cold, and/or it may expand on contact with hotmaterial (such as, over 150° F.), and preferably remains inactive beforea determined designed activation temperature, such as at about roomtemperatures. The coating may be repulpable, recyclable, and/orbiodegradable.

FIGS. 2 and 3 illustrate a container 101 with an outer wall of a die cutblank 102. The container 101 may be constructed as a double-wall cupassembly. The container 101 may be a cylindrical cup or container havingother geometrical configurations, including conical, rectangular, etc.The die cut blank may fully or partially cover the body of thecontainer. The die cut blank 102 may be an outer wall of the container101. The container 101 and die cut blank 102 may be integrated into acup 100 and the expandable material or adhesive may be applied betweenthe container body 101 and the die cut blank 102. The activatablematerial may additionally have adhesive properties and thus may form theonly attachment between the container and the blank. The die cut blank102 may be made of any nominal paper stock, including but not limitedto, natural single-face, white-topped single face, coated bleached topsingle-face or any combination of these. The die cut blank and/orcontainer may be repulpable, recyclable and/or biodegradable. The diecut blank 102 may include, for example, corrugated, flute corrugated orembossed grooves. The grooves may be in a vertical, diagonal, or otherdirection and may channel heat away from the hands.

The die cut blank 102 may be removable from the container or the die cutblank may be adhered to the container. For example, a one-piececontainer, such as a cup, may be manufactured 101 by laminating the diecut blank onto the container, using a hot melt and expandable materialto secure the die cut blank, or any other adhesive or sealing method.Alternatively, the thermally-activated material may be used to adherethe blank to the cup. If the die cut blank 102 is permanently attachedto the container 101 during manufacture (e.g., creating an integratedone-piece cup), it may increase the efficiency of using a thermal diecut blank by eliminating an assembly step by the commercial end-user.Further, it may decrease the amount of storage space required by thecommercial end-user, e.g., storing one item as opposed to two.

The die cut blank may remain open ended on one side or on opposingsides, which may permit airflow. For example, in FIG. 2, the containermay contain openings 210 near the top 212 of the integrated container100. The opening may be formed into the die cut blank, for example asholes, and the air flow may be created when the space between thecontainer 101 and the die cut blank 102 is expanded by the expandablematerial. Airflow may be further manipulated, for example, upward andaway from the holding fingers by corrugated, flute corrugated, or otherchannels in the die cut blank 102 or expandable material applicationpattern 216. For example, the pattern of application of the expandablematerial may create heat release channels 216.

FIG. 3 illustrates an alternate non-limiting example of how applicationof the expandable material may form openings 310 near the top 212 of thecontainer 101. The channels may be formed on expansion of the material.There may be openings on opposing ends of the container 101, such as atthe top 212 and the bottom 214. The openings may be formed by wrappingthe die cut blank on the container without completing the seal at thetop 212 or bottom 214.

FIG. 4 illustrates a cross section of a die cut blank 102 assembled withthe cup 101. This figure is meant to be illustrative and not limiting.The cup may be replaced with any container, for example, a press-formedtray, a soup tub, or a bulk beverage container. The die cut blank 102may have an inner face 406 and an outer face 404. An expandable materialmay be applied to the inner face 406, the outer face. 404 and/or to asurface between 402 the inner face 406 and the outer face 404. The innerface 406 and outer face 404 do not necessarily contain a space 402between. In another non-limiting example, the expandable material may beapplied between the container wall 101 and the die cut blank 102 and mayresult in an integrated container 100.

A thermally-expandable material 408 may be applied to an inner face 406of the die cut blank 102 in an inactive form. The inactivated material408 may be applied as a thin film that does not materially alter thethickness of the die cut blank 102. Applying the expandable material tothe inside of the die cut blank may also maintain the printability ofthe outer face of the die cut blank. If the inactivated expandablematerial 408 on the die cut blank 102 is assembled, for example, with astandard paper cup, it may maintain the slim profile of the cup.Maintenance of the slim profile may retain the efficient nestingqualities of a standard cup, allowing it to be efficiently cased, cratedand shipped.

The expandable material 408 may be activated and thereby expanded by,for example, adding hot liquid, beverage or food into the container 101.Activation may occur only at the consumption stage and not at theprocessing stage of the die cut blank, such that the die cut blank maybe shipped to the consumer with a substantially inactivated expandablematerial. For example, the activation point of the expandable materialmay be greater than about 120° F. and/or less than 60° F., such that theexpandable material may be activated only by the temperature of hotliquids, beverages, or food and not activated by ambient or bodytemperature. The activation may cause the expandable material to expandand “push back” the die cut blank 102 from the container 101 creating anincreased air gap. The air gap may create a thermal barrier between thehot beverage container 101 and the hand of the consumer. The activationmay also enhance the stiffness and/or rigidity of the container, whichmay allow for a reduction in the material or thickness of the containerwall. As described in more detail below, the coating may also beactivated, or at least partially activated, before reaching theconsumer.

The expandable material 408 may be applied to the die cut blank 102 inan unexpanded state. Expansion of the die cut blank may not occur untilactivated by adding hot fluid or solids, such as at the point ofserving. This may be different from expanding the material duringmanufacture of the die cut blank. Expansion during manufacture mayincrease the bulk of the die cut blank. The expandable material may becontrolled to effect nesting efficiency. The properties of the die cutblank may be further controlled by, for example but not limited to,combining a die cut blank constructed from fluted corrugate materialwith patterned application of expanded material to provide specificinsulation, air flow characteristics and container rigidity enhancement.For example, the corrugation and/or the pattern of expandable materialapplied to the die cut blank may direct heat convection upward, and maytherefore reduce heat transfer horizontally toward the holding hand ofconsumer. In other implementations, expansion may occur before shipping,such as before, during or after the manufacturing of the container.

FIG. 5 is an exemplary top view of a cross-section of a container 101assembled with a thermal die cut blank 102. This figure is illustrativeonly and not limiting. The expandable material 408 may be applied to theinner-face 406 of the die cut blank 102. For example, the expandablematerial 408 may be applied between the die cut blank 102 and the wallof the container 101 and may form an integrated two-layer cup withthermally-activatable insulated expandable material in between. Theexpandable material may include, for example, expandable microspheres502 dispersed in a binder or any other suitable material disclosed above504 and may include an adhesive property.

FIG. 6 illustrates an exemplary die cut blank 602. This drawing isillustrative and not meant to be limited to a size or shape. The sizeand shape may be adapted to the dimensions of any container. Anexpandable material 408 may be applied to the die cut blank 602. Theexpandable material may be applied by a number of methods, such as butnot limited to, a nozzle spray gun, printing, a slot coater, or othermethods, such as those described in more detail below. The expandablematerial 408 may be applied to the die cut blank 602, for example, on anin-line cup wrapping machine, in-line on a folder/gluer, or by othersuitable methods, such as off-line coating and drying. The expandablematerial 408 may be applied to the die cut blank 602 in any suitablepattern, such as but not limited to, banded, dotted, waved, squares,circles, diamonds, random, a combination of these or any other pattern.For example, the expandable material may be applied in a pattern thatmanipulates air flow and/or conducts heat, for example, verticallyupward away from the holding fingers. The expandable material may beapplied such that it forms channels, or expands to form channels onactivation. The channels may direct the natural convection. Theexpandable material 408 may fully or only partially cover the surfacebeing coated.

The coated die cut blank may be removably or permanently attached to acontainer or cup by, for example, wrapping the die cut blank around thecontainer. For example, a one-piece cup or container may be manufactured101 by laminating the die cut blank onto the container, using a hot meltand expandable material to secure the die cut blank, using an expandablematerial with adhesive properties, a combination of these or any otheradhesive or sealing method. If the die cut blank 102 is permanentlyattached to the container 101 during manufacture (for example, creatingan integrated one-piece cup), it may increase the efficiency of using athermal die cut blank by eliminating an assembly step by the commercialend-user. Further, it may decrease the amount of storage space requiredby the commercial end-user (storing one item as opposed to two). Theshape of the die cut blank in the drawing is not meant to be limiting.The shape of the die cut blank may be adapted to the shape of othercontainers, for example but not limited to, a soup tub, press-formedcontainer, or bulk beverage containers.

The die cut blank 602 may, optionally, contain in-seam hot-melt 604 orcold-set glue. If the expandable material 408 is also an adhesive, thein-seam hot-melt or cold-set 604 may be omitted. The in-seamhot-melt/cold-set glue 604 may be used in addition to the expandablematerial 408, such as, for bonding reinforcement. The die cut blank maybe applied to a cup by, for example, wrapping, laminating, or othermanufacturing processes.

FIGS. 7 through 11 illustrate other examples of a die cut blank 402.These examples are merely illustrative and not limiting. FIG. 7illustrates a die cut blank 602 with expandable material 408 applied ina pattern 709 to channel the release of heat. The die cut blank 602 maybe made of, for example, corrugated paper, such as but not limited tofluted corrugate. Convection may be manipulated by corrugation, thepattern of application of the expandable material, or in anothersuitable manner.

FIGS. 8 through 11 illustrate other possible, non-limiting examples ofpotential patterns of expandable material. The patterns of expandablematerial are represented by numbers 809, 909, 1009, and 1109,respectively. The expandable material may be applied in patterns otherthan those illustrated in FIGS. 7-11. The pattern of expandable material809, 909, 1009, and 1109, respectively, may vary in thickness and mayprovide graduated flow to channel heat to die cut openings. Die cutopenings are represented by numbers 814, 912, 1012, and 1112,respectively. Die cut openings may also be located and/or include shapessuch as illustrated by numbers 812, 914, 1014, and 1114. There may bedie cut openings at opposing ends of the blank, or only at one end. Theshapes of the die cut openings in FIGS. 8-11 are illustrative only andnot limiting. For example, the patterns of expandable material and theshape of the die cut openings may be so arranged as to manipulate airflow, for example but not limited to, creating a Venturi effect.

FIG. 12 is an illustrative example showing exemplary heat transfer. Thisexample is not meant to be limiting, but merely illustrative of possibleheat loss manipulation. Total heat loss of the system may be representedby the following equation:

Q ^(T)[Cal./second]=Q ₁ +Q ₂ +Q ₃ +Q ₄  1.

Where Q^(T) is the total heat loss. Q₁ 1204 may be the heat loss due towater evaporation. Q₂, Q₃, and Q₄, represented by 1202, 1206, and 1208,respectively, may represent the convectional and conductional heat loss.

The objective of keeping contents hot may be achieved by-minimizingQ^(T). The die cut blank may minimize Q^(T) by minimizing Q₂, Q₃, andQ₄. The low thermal conductivity of the expandable material may resultin much lower heat loss due to Q₂, Q₃, and Q₄.

The objective of preventing consumer flesh burns may be achieved by, forexample, minimizing Q₂, Q₃, and Q₄, especially Q₂, Q₃, while allowing Q₁and Q₄ to channel the unavoidable high heat flux (due to the hot liquid)vertically up or down This may be achieved by, for example, addingcorrugated grooves to the die cut blank. The grooves may be, forexample, in a generally vertical or diagonally tilted.

Non-limiting examples follow.

Example 1

Example 1 provides a graphical representation of how the expandablematerial may alter thermal conductivity. The temperature on the insideof a cup may be represented by Ti. The temperature on the outside of thecup may be represented by To. The top line, X, may represent a containerwithout the coated die cut blank. The second line. Y, may represent acontainer assembled with a coated die cut blank. This example mayillustrate that, in a container without a die cut blank coated with theexpandable material, the difference in the temperature inside versus theoutside of the container may be very small. In a container with a diecut blank coated with the temperature activated material, the differencein the temperature between inside and outside may be small when the hotfood or beverage is added to the container. However, the food orbeverage may activate the material, A, on contact, causing the materialto expand. When the material expands, the difference in temperatureTi−To, may increase.

Example 2

Example 2 illustrates temperature sensory comparison of various die cutblank materials coated with the thermally-expandable material comparedto without the thermally-expandable material. The following experimentis for illustration only and is not limiting, other experimental resultsmight be obtained.

A thermally, or other, expandable material may be applied to die cutblanks made of various materials, such as but not limited to paper,paperboard, and fluted corrugated paper. Each die cut blank may bewrapped around a container, such as a cup. The cup may be filled withhot water. The cups may then be handled with bare hands and a comparisonmade between the sensory responses to the two conditions. In each test,the cups with coated die cut blanks were less “hot” to the touch thanthose with uncoated die cut blanks. Expansion occurred within a fewminutes of pouring hot water into the cup.

Example 3

Coatings may be applied by smearing the coating to a single face medium.The coating may be expanded when wet using a MASTER-MITE 120 V, 475 Wheat gun at 600 degrees F.

Example 4

Coatings may be applied to the outside of a 12 Oz cup and allowed toair-dry overnight. The next day, 190 degree F. hot water may be pouredinto the cup. Noticeable expansion may be observed shortly after filingthe 190 degree F. hot water into the cup. Lids may be placed on the cup,and after 7 minutes more expansion may be observed, but still partialexpansion. A benefit of post-heat activation may be that the hotter theliquid the more the coating expands.

Example 5

Coating was applies to a cup. A 250 W IR heater manufactured by FisherScientific model no. 11-504-50 may be used to heat the coating.Expansion may be slow when the lamp is six inches away from the coatingand immediate when one inch away from the coating. Excess heat and timemay cause coating deformation from the substrate surface.

Example 6

Coating may be applied to paper, which may them be wrapped around apaper cup after the coating is allowed to air dry. Heat from a heat gunmay be used to heat the part of the coating indirectly through the papershell for one minute. The coating expanded. Another part of the unheatedcoating may be heated under an IR lamp through the paper. The coatingexpanded.

FIG. 13 is a side cutaway view of a double wall container 101. Thedouble wall container 101 may provide a jacket of air between an outerwall 1300 and contents 1302, such as a hot or cold beverage or food, ofthe container 101. The air jacket may provide thermal insulation asmeasured by an outside surface temperature T₀. The air jacket maypartially or completely surround the container 101. When the container101 is grabbed, a pressure exerted on the outer wall 1300 may act tocollapse the outer wall 1300 at pressure points to reduce the air jacketand potentially initiate contact with an inner wall 1304 of thecontainer 101. The air jacket may collapse under pressure points and maygive a sense of low rigidity, and the contact may create hot spots onthe outer wall 1300 if a thermally expandable coating 216 is not used.

If a sufficient amount of coating 216 is used, the coating 216 may actto provide rigidity without compromising the thermal insulation of theair jacket to the outer wall 1300 such that the outer wall 1330 does notcollapse, completely or partially. The coating 216 may add mechanicalstrength to the container 101. Lighter weight materials may be used toproduce the container 101 due to mechanical strength added by thecoating 216, such that the source of a substrate forming the container101 may be reduced. The coating 101 may be applied in spots, such asdots, or another pattern, either on the inner wall 1304, the outer wall1300, or both, such that the coating 216 provides an air gap andprevents the container 101 from collapsing under holding pressure. Thecoating 101 may also provide a rigid feel to the user, while allowing areduction of the substrate material.

FIG. 14 is a block diagram of an exemplary process for applying amicro-particle coating to substrates. The process may include applying amicrosphere or other expandable coating to any of a substrate, die cutblank, container, sleeve, catering trays, double-wall cups, press-formedtray, soup tub and bag-in-the box containers. The process may includeinline 1400 and off-line 1410 procedures. The inline procedure 1400 mayinclude stacking stations 1420, manufacturing stations 1430, andpackaging stations 1440 used for the manufacturing of the container frompaper or die cut stock. The stacking, manufacturing and packagingstations may be completely automated and/or include manual stations.

Coating application processes may occur in-line 1400 or offline 1410, atthe same or another facility. In-line application may include theapplication of the coating at one or more of the stacking stations 1420,manufacturing stations 1430, and packaging stations 1440. The coatingmay be applied in various ways, including but not limited to brushes,sponges, printing, a nozzle, spray, and a slot die coater. Any of theseapplications, or various combinations of them, may occur in-line 1400 oroffline 1410, where the off-line process may occur before the stackingstage 1420.

Application with a brush or brushes may occur by feeding the coatingwith pressure through a tube to the brush. The brush may be manufacturedfrom different materials such as horse hair or synthetic materials. Thebrush may include hollow filaments such that the coating is appliedthrough the filaments. The brush may apply a swatch or pattern of thecoating. The amount of coating to the brush may be controlled such thatthe amount of coating applied to the substrate may be metered. As anillustrative and not limiting example, the amount may be controlled suchthat a 1/64^(th) inch layer of coating is applied, which may expand to1/16 or 1/32 of an inch, or the distance of the gap between an inner andouter layer of a double-wall cup. It may be preferable that the coatingdoes not deform a shape of the outer layer once expanded. The coatingmay be distributed in a uniform or varying pattern. The brush may beused for broader applications, such as to coat the inside of abag-in-the-box container.

Application with a printing press may occur by running substratesthrough rollers. The substrates may be roll or web form of paper stock,or alternatively in sheet form. The coating may be press applied inspots or patterns or with full coverage, depending on an implementation.

In FIG. 15, spray nozzles 1500 may be used to apply a coating 1510 to asubstrate 1520. The nozzles may diffuse the coating to apply a thin,uniform layers of the coating on the substrate. One or more spraynozzles may be used to form continuous or interrupted patterns of thecoating. The nozzles may be arranged such that the applied coatingsoverlap, are side-by-side and/or are separated by a space. The spray maybe metered to control a thickness of the applied coating. The nozzle mayalso be positioned to direct spray of the coating onto designatedportions of the substrate, such as at a corner.

In FIG. 16, non-spray nozzles 1600 may be used to apply a stream 1610 ofcoating to the substrate 1620. The stream may be metered through thenozzle to apply a precise amount. The nozzle may to sized to control aspecified width and height of the stream 1610. Flow from the nozzles maybe turned on and off to accommodate a specified pattern of the coatingto the substrate.

In a trough or a dip coating application, substrates may be movedthrough the trough that contains coating material. One or both sides ofthe substrate may be run through the trough. A thickness of the coatingbeing applied to the trough may be controlled by how long the substratesits in the material. A temperature of the coating and substrate may becontrolled to activate or not activate the expandable coating during thecoating process. A control blade may be used to meter off excesscoating. The substrates may be belt fed though the through orindividually held in the through.

With any of the above application processes, and with any other process,the applied coating may be dried or set, such as by applying or blowingcool air or warm air without activating the coating, if it is desired toexpand the coating in a later process, such as during manufacturing orat the time of consumer use. The coating may also be expanded aftermanufacturing and before consumer use, such as at the stacking station1440. The coating may be expanded before or after stacking thecontainers.

Coated or uncoated blanks may be fed to the stacking station 1420. Thecoating may be applied during in-line or off-line processing. If appliedin-line, the coating may be allowed to dry before the cups, sleeves,containers, etc. are formed, or they may be formed while the coating iswet. Depending on the properties of the coating, it may take a couple ofseconds to several minutes to dry. The coating may be activated duringthe in-line manufacturing or afterwards, such as at the consumer stage.To activate the coating in-line, any or all of infrared (IR), air,convection or conductive heating methods may be used. The coating maytake a couple of seconds to several minutes to fully expand. Forexample, a mandrel, which holds a container from the inside of thecontainer, and/or a collar, which holds a cup from the outside of thecontainer, may be used to apply heat to expand the coating during thecontainer manufacturing process. If a wet or partially dry coatingcontacts the mandrel during process, the mandrel may be manufactured toinclude a non-stick material, such as TEFLON to prevent sticking ortransfer of the coating onto the mandrel. Lower activation temperaturesmay be preferred if the activation occurs in-line. By activating thecoating, the coating expands to form a reinforced air gap. The coatingmay be partially expanded during manufacturing of the container, andthen the expansion may continue to the consumption stage.

As mentioned, use of the coating may help to reduce the thickness ofsubstrate needed to make the container, sleeves, etc., while maintaininga better rigid feel to the consumer. The coating may also improveinsulation properties of the container, and to help keep the beveragesor foods warm or cold longer, depending on the application. Thesubstrates may be made of natural fibers, synthetic or both, such as SBS(solid bleached sulfate) paper board or box board. A sleeve materials,such as liner and medium, may be produced of 15 LB/3000 ft² to 100LB/3000 ft² material, and preferably 18 LB/3000 ft to 50 LB/3000 ft².The caliper of the paper substrate for hot or cold cups, soup tub,press-formed container and other non-corrugated containers may rangefrom 9 point to 24 point, and preferably 10 point to 24 point, where apoint is equal to 1/1000 inch.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof the invention.

We claim:
 1. A double-wall container, comprising: an inner wall; anouter wall attached to the inner wall, where the inner wall and theouter wall form an air gap therebetween; and an expandable coatingpositioned between the inner wall and the outer wall.
 2. The double-wallcontainer of claim 1 where the expandable coating comprises expandablemicrospheres.
 3. The double-wall container of claim 1 where theexpandable coating provides thermo insulation between the inner wall andthe outer wall.
 4. The double-wall container of claim 1 where theexpandable coating provides a rigidness to the outer wall.
 5. Thedouble-wall container of claim 1 where the outer wall is comprised of apaper stock.
 6. The double-wall container of claim 5 where theexpandable coating accommodates a reduction in a weight of the paperstock.
 7. The double-wall container of claim 1 where the expandablecoating is activated to expand by a hot temperature.
 8. The double-wallcontainer of claim 1 where the expandable coating is applied is a dottedpattern.
 9. A method of making a double-wall container, comprising:providing a first substrate to form a container, providing a secondsubstrate to form an outer wall of the container; coating the secondsubstrate with a thermally expandable material; attaching the secondsubstrate to the container to form the outer wall; forming thedouble-wall cup from the container and the outer wall; and applying theexpandable coating between the container and the outer wall.
 10. Themethod of claim 9 where the expandable coating is applied before formingthe double-wall cup.
 11. The method of claim 9 where the expandablecoating is applied during the forming of the double-wall cup.
 12. Themethod of claim 9 further comprising expanding the expandable coatingduring the forming of the double-wall cup.
 13. The method of claim 9further comprising expanding the expandable coating after forming thedouble-wall cup.
 14. The method of claim 9 where the coating is appliedis a dotted pattern.
 15. A container, comprising: a side wall having aninner surface and an outer surface; at least one of the inner surface orthe outer surface of the side wall being at least partially coated by alayer of an expandable material; and the material adapted to be expandedto provide thermal insulation.
 16. The container of claim 15, where theexpandable material comprises expandable microspheres.
 17. The containerof claim 15 where the side wall comprises the side of a sleeve for acup.
 18. The container of claim 15 where the side wall comprises theside of a container for holding a bag.
 19. The container of claim 15where the material is expanded upon manufacturing.
 20. The container ofclaim 15 where the material is expanded by a beverage or food.
 21. Thecontainer of claim 15 where the expandable material is thermallyexpandable.